This invention relates generally to the dispensing of materials such as food sauces and deals more particularly with an improved disk valve which controls the flow of materials that are dispensed from cartridge type dispensers.
In fast service restaurants and other retail food establishments, food sauces of various types must be dispensed in a large number of portions each containing a relatively small quantity of sauce. The sauces are usually a mayonnaise base salad dressing with various spices and other ingredients added to provide flavoring and/or texture. Because they have a consistency similar to mayonnaise, the food sauces are semi-solid and can be made to flow without great difficulty. Accordingly, it has proven to be convenient to package a wide variety of food sauces in cartridges from which the sauces are dispensed by hand held dispensing guns similar to caulking guns.
The dispensing gun includes a plunger which is advanced incrementally an identical distance each time its operating trigger is squeezed. The plunger in turn advances a plug in one end of the cartridge, and this causes a measured amount of sauce to be extruded out through a cross hair cut in the opposite end of the cartridge which serves as a dispensing valve. Reference may be made to U.S. Pat. No. 4,432,473 for a more thorough discussion of this type of dispensing cartridge and gun.
Although this manner of dispensing food sauces has been satisfactory for the most part, it has not been wholly free of problems. The end disk which serves as the dispensing valve is typically made from low density polyethylene which is slitted in a cross hair pattern to provide leaves or vanes which are normally closed but which open when internal pressure is generated by the advancing plunger. With polyethylene end disks, the size of the valve is based on the relationship between the viscosity of the product which is being dispensed and the "memory" of the polyethylene (i.e., its ability to return to its undeformed state following removal of the deforming force). If the valve is too large, the vanes do not exert sufficient back pressure to achieve an even and predictable product flow. As a consequence, the sauce oozes through the valve and is not cleanly cut off at the end of the dispensing operation, thus tending to "string" the food sauce as the dispensing gun in moved from one sandwich to another. Conversely, a valve that is too small results in excessive back pressure, and the sauce squirts out with so much force that it splatters and at times can displace lettuce and other condiments from the sandwich. Because only one valve is used, the product is dispensed over only a relatively small area and the dispensing operation suffers for this reason also.